Constituitional Isomerism

1. Constitutional (Structural) Isomerism

Isomers have
o Same molecular formula 

01 Multiple Choice

2. Chain Isomerism

Isomers have
o Different structural formula

2.1. C4H10O (Consider ether only)

Ethoxyethane	1-Methoxypropane	2-Methoxypropane

2.2. C5H12

Molecular formula: C₅H₁₂

Pentane	Isopentane	Neopentane

2.3. C6H14

Hexane	2-Methylpentane	3-Methylpentane
2,2-Dimethylbutane	2,3-Dimethylbutane

3. Position Isomerism

o Same functional group that differ in its position

3.1. C3H8O (Consider alcohol and non-cyclical compound only)

Molecular formula: C₃H₈O

1-Propanol	2-Propanol

3.2. C4H10O (Consider alcohol and non-cyclical compound only)

Chain isomerism	Position isomerism	Position isomerism
1-Butanol	2-Butanol	2-Methyl-2-propanol
2-Methyl-1-propanol

3.3. C5H10 (Consider alkene and non-cyclical compound only)

1-Pentene	2-Methyl-1-butene	3-Methyl-1-butene
cis trans
2-Pentene	2-Methyl-2-butene

3.4. C7H7Cl (Contains a benzene ring)

Molecular formula: C₇H₇Cl

(Chloromethyl) benzene	1-Chloro-3-methylbenzene	1-Chloro-4-methylbenzene	1-Chloro-2-methylbenzene

3.5. C8H10 (Contains a benzene ring)

Ethylbenzene	1,2-Dimethylbenzene (o-Xylene)	1,4-Dimethylbenzene (p-Xylene)	1,3-Dimethylbenzene (m-Xylene)

4. Functional Group Isomerism

Isomers have
o Different functional group

4.1. C2H6O

Molecular formula: C₂H₆O

Ethanol	Methoxymethane

4.2. C3H6O

Molecular formula: C₃H₆O

Acetone	Propionaldehyde

4.3. C3H6O2

Propanoic acid	Methyl ethanoate	Ethyl methanoate